\documentclass{minimal}
\usepackage{lipsum}
\usepackage{pgfplots}
\usepgfplotslibrary{dateplot}

\newsavebox{\measuredSize}
\newcommand{\resizeToWidth}[2]{%
	\pgfmathsetmacro{\pgfplotswidth}{#2}%
	\begin{lrbox}{\measuredSize}#1\end{lrbox}%
	\pgfmathsetmacro{\pgfplotswidth}{2*\pgfplotswidth-\wd\measuredSize}%
	#1%
}

\newcommand{\inputPlot}{%
	\begin{tikzpicture}
		\begin{axis}
			[
				height=5cm,
				width=\pgfplotswidth,
				yticklabel style={align=right,inner sep=0pt,xshift=-0.3em},
				grid=both,
				max space between ticks=50,
				minor x tick num=4,
				minor y tick num=4,
				tick style={semithick,color=black},
				date coordinates in=x,
				xticklabel=\day.\month.
			]
			\addplot[color = black, mark=diamond*] coordinates{
					(2009-08-07, 98) (2009-08-09, 92) (2009-08-12, 94) (2009-08-15, 87) (2009-08-19, 82) (2009-08-26, 65) (2009-08-29, 54) (2009-09-02, 31)
				};
		\end{axis}
	\end{tikzpicture}%
}

\begin{document}
\setlength{\parindent}{0ex}

\lipsum[1]\vspace*{2ex}

\resizeToWidth{\inputPlot}{\textwidth}

\vspace*{2ex}\lipsum[2]
\end{document}
